Do you think Hamlet was in love with Ophelia?
Yes. In fact, most of the keys to this very complex relationship comes in the "To be or not to be" scene, Act 3, Scene 1.
Ophelia, remember, has been told by Polonius that she can't see Hamlet - though she admits that he has been making advances towards her. In that scene, though, she makes out that it's all been one-sided, when, in fact, it clearly hasn't. There has been a realtionship, as she reveals when she gives him back his love tokens, his "remembrances", which he claims he never gave her.
My honour'd lord, you know right well you did,
And with them words of so sweet breath compos'd
As made the things more rich. Their perfume lost,
Take these again; for to the noble mind
Rich gifts wax poor when givers prove unkind.
How has he proved unkind? Is it because, since seeing the ghost, he hasn't seen her or spent any time with her - or called it off? Is it because she hasn't been anywhere near him? We're not sure. But, just as Hamlet becomes hugely, hysterically emotional at the graveyard scene, Ophelia seems to provoke or elicit a massive angry, emotional response from Hamlet even in this scene:
God hath given you one face, and you make yourselves another. You jig, you amble, and you lisp; and nickname God's creatures and make your wantonness your ignorance.
There's a lot of baggage in this scene, and the language is charged and emotional. What specifically happened in the relationship is unclear and difficult to tease out of the text - there are lots of possibilities for interpretation. But one thing is clear:
I did love you once.
Indeed my lord, you made me believe so.
The two previous answers are very well argued but I think you have to enter the usual caveat when considering any aspect of Hamlet's behaviour: to what extent can we believe what we are seeing and hearing? This is because, in the first place, Hamlet's mental state is open to question and, second, because he is such an actor. To me, Hamlet's treatment of Ophelia in the play is not indicative of strong love, whatever about his words, and even at her burial I find myself wondering whether this isn't just another act, something to out-Laertes Laertes with. The last point made in the robertwilliam answer above is key in my view: Hamlet may have been in love with Ophelia before the play begins (so to speak) but, for whatever reasons, that love has very much become secondary in his life when we see him on stage.
Hamlet was most certainly in love with Ophelia. Unfortunately, she is the victim of circumstance because Hamlet is sworn to avenge his father's murder and their former love is as past as his "former sanity" was. When Ophelia approaches Hamlet after the (3.1) soliloquy, he says "soft you now, the fair Ophelia,' and we hear a soft loving tone escape him. It is in the ensuing "nunnery" speech where he realizes she's a pawn for Polonius and Claudius, that marriages are delicate institutions, and the nature of existence: sin and the temptations of sin. This is why he gets so furious, because his former "love" seems betrayed. Furthermore, when Ophelia is buried, we have no reason to doubt that the hyperbolic protestations of love are not genuine.
To the celestial, and my soul's idol, the most beautified Ophelia
Doubt thou the stars are fire;
Doubt that the sun doth move;
Doubt truth to be a liar;(125)
But never doubt I love.
O dear Ophelia, I am ill at these numbers; I have not art to reckon my groans. But that I love thee best, O most best, believe it. Adieu. Thine evermore, most dear lady, whilst this machine is to him,